Base station and method for implementing an adaptive closed-loop mimo and open-loop mimo technique in a wireless communication system

Abstract

A base station and a method are described herein that implement an adaptive closed-loop MIMO and open-loop MIMO technique which accounts for all channel conditions and improves the performance of communications with a user equipment. In one example, the base station and method analyze a current user equipment report and a previous user equipment report received from a user equipment to determine if at least one channel condition parameter has a rate of change greater than a corresponding at least one threshold and if yes then use an open-loop MIMO technique and if no then use a closed-loop MIMO technique when interacting with the user equipment.

1 . A base station which has multiple antennas and also implements an adaptive closed-loop multiple input multiple output (MIMO) and open-loop MIMO technique, the base station comprising:
 a receiver that receives user equipment reports over a period of time from a user equipment;   a processor; and   a memory that stores processor-executable instructions therein where the processor interfaces with the memory and executes the processor-executable instructions to enable the following:
 analyze a current user equipment report and a previous user equipment report received from the user equipment to determine if at least one channel condition parameter has a rate of change greater than a corresponding at least one threshold and if yes then use the open-loop MIMO technique when interacting with the user equipment and if no then use the closed-loop MIMO technique when interacting with the user equipment; and 
   a transmitter that sends a message to the user equipment indicating whether currently utilizing the open-loop MIMO technique or the closed-loop MIMO technique to interact with the user equipment.   
     
     
         2 . The base station of  claim 1 , wherein the at least one channel condition parameter is an average speed of the user equipment. 
     
     
         3 . The base station of  claim 1 , wherein the at least one channel condition parameter is a frequency location change rate associated with the user equipment. 
     
     
         4 . The base station of  claim 1 , wherein the at least one channel condition parameter is a Channel Quality Information (CQI) change rate associated with the user equipment. 
     
     
         5 . The base station of  claim 1 , wherein the at least one channel condition parameter is a Pre-Encoding Matrix Indicator (PMI) change rate associated with the user equipment. 
     
     
         6 . The base station of  claim 1 , wherein the user equipment reports include one or more of following:
 a rank information (RI), a L-bit map, a plurality of Channel Quality Information (CQIs), a wideband Pre-Encoding Matrix Indicator (PMI), and a wideband CQI;   a rank information (RI), a L-bit map, a plurality of PMIs, a wideband PMI, and a wideband CQI; and   a rank information (RI), a L-bit map, a plurality of CQIs, and a wideband CQI.   
     
     
         7 . The base station of  claim 1 , wherein the processor executes the process-executable instructions to perform the analyze operation as follows:
 start a cycle and wait for a transmit time interval (TTI) to pass;   determine if a monitoring period passed, where the monitoring period has a duration corresponding to a predetermined number of TTIs;   if result of the first determine step is yes, then:
 compare the current user equipment report and the previous user equipment report to obtain the at least one channel condition parameter; 
 determine if the at least one channel condition parameter has a rate of change greater than the corresponding at least one threshold; 
 if the result of the second determine step is yes, then set a mobile velocity flag to a first value, wait for next TTI to pass, and return to the first determine step; 
 if the result of the second determine step is no, then set a mobile velocity flag to a second value, wait for next TTI to pass, and return to the first determine step; 
   if the first determine step is no, then determine if the mobile velocity flag is set to either the first value or the second value;
 if the mobile velocity flag is set to the first value, then use the open-loop MIMO technique, wait for the next TTI to pass, and return to the first determine step; 
 if the mobile velocity flag is set to the second value, then use the closed-loop MIMO technique, wait for the next TTI to pass, and return to the first determine step. 
   
     
     
         8 . A method in a base station which has multiple antennas for implementing an adaptive closed-loop multiple input multiple output (MIMO) and open-loop MIMO technique, the method comprising the steps of:
 receiving user equipment reports over a period of time from a user equipment;   analyzing a current user equipment report and a previous user equipment report received from the user equipment to determine if at least one channel condition parameter has a rate of change greater than a corresponding at least one threshold and if yes then use the open-loop MIMO technique when interacting with the user equipment and if no then use the closed-loop MIMO technique when interacting with the user equipment; and   sending a message to the user equipment indicating whether currently utilizing the open-loop MIMO technique or the closed-loop MIMO technique to interact with the user equipment.   
     
     
         9 . The method of  claim 8 , wherein the at least one channel condition parameter is an average speed of the user equipment. 
     
     
         10 . The method of  claim 8 , wherein the at least one channel condition parameter is a frequency location change rate associated with the user equipment. 
     
     
         11 . The method of  claim 8 , wherein the at least one channel condition parameter is a Channel Quality Information (CQI) change rate associated with the user equipment. 
     
     
         12 . The method of  claim 8 , wherein the at least one channel condition parameter is a Pre-Encoding Matrix Indicator (PMI) change rate associated with the user equipment. 
     
     
         13 . The method of  claim 8 , wherein the user equipment reports include one or more of following:
 a rank information (RI), a L-bit Map, a plurality of Channel Quality Information (CQIs), a wideband Pre-Encoding Matrix Indicator (PMI), and a wideband CQI;   a rank information (RI), a L-bit map, a plurality of PMIs, a wideband PMI, and a wideband CQI; and   a rank information (RI), a L-bit map, a plurality of CQIs, and a wideband CQI.   
     
     
         14 . The method of  claim 8 , wherein the analyzing step further comprises:
 starting a cycle and waiting for a transmit time interval (TTI) to pass;   determining if a monitoring period passed, where the monitoring period has a duration corresponding to predetermined number of TTIs;   if result of the first determining step is yes, then:
 comparing the current user equipment report and the previous user equipment report to obtain the at least one channel condition parameter; 
 determining if the at least one channel condition parameter has a rate of change greater than the corresponding at least one threshold; 
 if the result of the second determining step is yes, then setting a mobile velocity flag to a first value, waiting for next TTI to pass, and returning to the first determining step; 
 if the result of the second determining step is no, then setting a mobile velocity flag to a second value, waiting for next TTI to pass, and returning to the first determining step; 
   if the first determining step is no, then determining if the mobile velocity flag is set to either the first value or the second value;
 if the mobile velocity flag is set to the first value, then using the open-loop MIMO technique, waiting for the next TTI to pass, and returning to the first determining step; 
 if the mobile velocity flag is set to the second value, then using the closed-loop MIMO technique, waiting for the next TTI to piss, and returning to the first determining step. 
   
     
     
         15 . A wireless communication system comprising:
 a user equipment that sends user equipment reports over a period of time;   base station which has multiple antennas and also implements an adaptive closed-loop multiple input multiple output (MIMO) and open-loop MIMO technique, the base station comprising:
 a receiver that receives the user equipment reports from the user equipment; 
 a processor; and 
 a memory that stores processor-executable instructions therein where the processor interfaces with the memory and executes the processor-executable instructions to enable the following: 
 analyze a current user equipment report and a previous user equipment report received from the user equipment to determine if at least one channel condition parameter has a rate of change greater than a corresponding at least one threshold and if yes then use the open-loop MIMO technique when interacting with the user equipment and if no then use the closed-loop MIMO technique when interacting with the user equipment; and 
   a transmitter that sends a message to the user equipment indicating whether currently utilizing the open-loop MIMO technique or the closed-loop MIMO technique to interact with the user equipment.   
     
     
         16 . The wireless communication system of  claim 15 , wherein the at least one channel condition parameter includes one or more of following:
 an average speed of the user equipment;   a frequency location change rate associated with the user equipment;   a Channel Quality Information (CQI) change rate associated with the user equipment; and   a Pre-Encoding Matrix Indicator (PMI) change rat associated with the user equipment.   
     
     
         17 . The wireless communication system of  claim 15 , wherein the user equipment reports include one or more of following:
 a rank information (RI), a L-bit map, a plurality of Channel Quality Information (CQIs), a wideband Pre-Encoding Matrix Indicator (PMI), and a wideband CQI;   a rank information (RI), a L-bit map, a plurality of PMIs, a wideband PMI, and a wideband CQI; and   a rank information (RI), a L-bit map, a plurality of CQIs, and a wideband CQI.   
     
     
         18 . The wireless communication system of  claim 15 , wherein the processor executes the process-executable instructions to perform the analyze operation as follows:
 start a cycle and wait for a transmit time interval (TTI) to pass;   determine if a monitoring period passed, where the monitoring period has a duration corresponding to a predetermined number of TTIs;   if result of the first determine step is yes, then:
 compare the current user equipment report and the previous user equipment report to obtain the at least one channel condition parameter; 
 determine if the at least one channel condition parameter has a rate of change greater than the corresponding at least one threshold;
 if the result of the second determine step is yes, then set a mobile velocity flag to a first value, wait for next TTI to pass, and return to the first determine step; 
 if the result of the second determine step is no, then set a mobile velocity flag to a second value, wait for next TTI to pass, and return to the first determine step; 
 
   if the first determine step is no, then determine if the mobile velocity flag is set to either the first value or the second value;
 if the mobile velocity flag is set to the first value, then use the open-loop MIMO technique, wait for the next TTI to pass, and return to the first determine step; 
 if the mobile velocity flag is set to the second value, then use the closed-loop MIMO technique, wait for the next TTI to pass, and return to the first determine step.